In such a drive system, the electric motor usually acts to regulate the flow rate of fuel, and no additional regulator is provided on the fuel feed line to the turbine engine, since that would be redundant.
Furthermore, in spite of the very great reliability of present-day electrical systems, it is always possible that an electrical failure will occur in flight on the electric motor driving the pump, or indeed on the electricity generator that powers the pump (the assembly constituted by one or more electric motors, and their electricity power supply means being referred to herein as the electrical system).
To mitigate such a possibility, and as described in French patent FR 02/09028, emergency means are provided for backing up the electrical system, such as air turbine assistance means. The drive system thus includes an air turbine that can be fed with a flow of air bled from a compressor of said turbine engine in order to drive said accessory.
In order to be able to use such an air turbine, the drive system includes an on/off valve located in the air supply line upstream from the turbine. Providing the air pressure is sufficient, opening the valve enables the turbine to be set into rotation and thus causes the fuel pump to rotate.
Nevertheless, in the event of a failure of the electrical system, it is the air turbine on its own that drives the fuel pump. Unfortunately, no means are provided for controlling the speed of the air turbine. That is why, under such circumstances, the air turbine, and consequently the fuel pump, are no longer under control, which can lead to problems in piloting the vehicle.
More generally, the present invention relates to a system for driving a fuel pump in a turbine engine, said system comprising an electric motor, an electronic control unit, and fluid flow assistance means controlled by a control valve.
The fluid flow assistance means comprise additional motor means driven by a flow of fluid (pneumatic or hydraulic) suitable for assisting and/or replacing the electric motor(s) for driving the pump.